| The bonding strength between film and substrate is an important criteria for evaluating the quality of the film and substrate system, which determines the performance and the reliability of the systems.In this paper, the interface shear strength between films and substrates were evaluated by using a substrate straining method.Specimens were thermal oxidized in an air furnace at 500℃and 800℃for an hour firstly. After tensile loading, it was found that the fracture morphology of the TiOx film depended upon the bonding strength of the interface. A stronger bonding strength , at least 970 MPa ,of the TiOx/Ti system heat treated at 500℃was detected, and the most of the cracks in the TiOx films were aligned at a direction of±45o to the tensile axis. Cracks in the film of TiOx/Ti system heat treated at 800℃showed periodicity and were perpendicular to the tensile axis and the bonding strength of the system was calculated to be at most 495 MPa.Specimens prepared by sol-gel method were also evaluated in this paper by substrate straining method. With the thickness increasing, the interface bonding strengths were decreasing, but still in the same magnitude. what have to point out is the results are obviously larger than the true values.ANSYS software was used to discuss the affection of coating's thickness and elastic modular ratios. The results shows that substrate straining method fits for systems with thin and high elastic modular films specially.
|
PDF Full Text Request